1. Field of the Invention
The present invention relates to a dielectric ceramic composition and a multilayer ceramic capacitor using the same, and more particularly, to a dielectric ceramic composition, which can be sintered at a low temperature as well as achieve a high dielectric constant with excellent thermal stability, and a multilayer ceramic capacitor using the same.
2. Description of the Related Art
Recently, along with rapid development of electric and electronic appliances focused on miniaturization, light weight, high performance and so on, multilayer ceramic capacitors used therein are also facing demands for smaller size and larger capacitance. To achieve smaller size and larger capacitance, dielectric layers of such a multilayer ceramic capacitor are getting thinner. At present, a dielectric layer having a thickness of 3 μm or less is also demanded. Producing thinner dielectric layers needs dielectric powder and accessory additives where grain growth can be suppressed in sintering. Furthermore, thinner dielectric layers can be produced more easily when dielectric constant is higher compared to particle size of sintering material.
To produce a multilayer ceramic capacitor using thin dielectric layers, it is necessary to employ a dielectric composition sinterable at a temperature not exceeding 1,200° C. When a dielectric composition is sintered at a high temperature of 1,300° C. or more, internal electrodes tend to conglomerate, thereby lowering the capacitance of a ceramic capacitor while raising short-circuit ratio. Producing thin dielectric layers and stacking them by a greater number to obtain a high capacitance may give severe adverse influences to capacitance change at high temperature (thermal stability of capacitance).
Japanese Patent Application Publication No. 2000-311828 discloses a dielectric ceramic composition for a multilayer ceramic capacitor satisfying X5R and X7R characteristics. The dielectric ceramic composition proposed in this document contains a main component of BaTiO3 and sub-components such as Cr2O3. A multilayer ceramic capacitor produced using the dielectric magnetic composition has advantages such as small aging rate of capacitance and long accelerated life of Insulation Resistance (IR). However, the dielectric composition disclosed in this document has a sintering temperature of up to 1,270° C., and thus is hardly applicable to produce ultra thin dielectric layers of a multilayer ceramic capacitor.